ob: :file and :file-ext no longer imply :results file

* lisp/ob-core.el (org-babel-execute-src-block): ":results file" must
  be specified in order to return a file.
(org-babel-merge-params): :file and :file-ext no longer imply :results
file.
* testing/lisp/test-ob.el (test-ob/indented-cached-org-bracket-link):
(test-ob/result-file-link-type-header-argument):
(test-ob/result-graphics-link-type-header-argument): Update tests.

Deducing the results from some other arguments is not obvious.
Moreover, it prevents users from setting, e.g., :file-ext, in a node
property, as every block would then create a file.

Reported-by: Alex Fenton <alex@pressure.to>
<http://lists.gnu.org/r/emacs-orgmode/2018-05/msg00469.html>

3 files changed, 37 insertions, 25 deletions

diff --git a/etc/ORG-NEWS b/etc/ORG-NEWS
index dbe3c13..aa1b774 100644
--- a/etc/ORG-NEWS
+++ b/etc/ORG-NEWS
@@ -14,6 +14,12 @@ Please send Org bug reports to mailto:emacs-orgmode@gnu.org.
 
 ** Incompatible change
 
+*** ~:file~ header argument no longer assume "file" ~:results~
+
+The "file" ~:results~ value is now mandatory for a code block
+returning a link to a file.  The ~:file~ or ~:file-ext~ header
+arguments no longer imply a "file" result is expected.
+
 *** Plain numbers are hours in Column View mode
 
 See [[git:3367ac9457]] for details.
diff --git a/lisp/ob-core.el b/lisp/ob-core.el
index 5a902d2..7b7b314 100644
--- a/lisp/ob-core.el
+++ b/lisp/ob-core.el
@@ -694,7 +694,8 @@ block."
 			       (not (listp r)))
 			  (list (list r))
 			r)))
-	      (let ((file (cdr (assq :file params))))
+	      (let ((file (and (member "file" result-params)
+			       (cdr (assq :file params)))))
 		;; If non-empty result and :file then write to :file.
 		(when file
 		  ;; If `:results' are special types like `link' or
@@ -2624,19 +2625,6 @@ parameters when merging lists."
 				  results
 				  (split-string
 				   (if (stringp value) value (eval value t))))))
-	  (`(,(or :file :file-ext) . ,value)
-	   ;; `:file' and `:file-ext' are regular keywords but they
-	   ;; imply a "file" `:results' and a "results" `:exports'.
-	   (when value
-	     (setq results
-		   (funcall merge results-exclusive-groups results '("file")))
-	     (unless (or (member "both" exports)
-			 (member "none" exports)
-			 (member "code" exports))
-	       (setq exports
-		     (funcall merge
-			      exports-exclusive-groups exports '("results"))))
-	     (push pair params)))
 	  (`(:exports . ,value)
 	   (setq exports (funcall merge
 				  exports-exclusive-groups
diff --git a/testing/lisp/test-ob.el b/testing/lisp/test-ob.el
index 095f66a..28a7355 100644
--- a/testing/lisp/test-ob.el
+++ b/testing/lisp/test-ob.el
@@ -30,7 +30,7 @@ should still return the link."
      (org-test-with-temp-text
 	 "
 * Test
-  #+<point>BEGIN_SRC emacs-lisp :file test.txt :cache yes
+  #+<point>BEGIN_SRC emacs-lisp :results file :file test.txt :cache yes
     (message \"test\")
   #+END_SRC"
        ;; Execute twice as the first time creates the cache.
@@ -1003,30 +1003,48 @@ trying to find the :END: marker."
 The file is just a link to `:file' value.  Inhibit non-empty
 result write to `:file' value."
   (org-test-with-temp-text "
+<point>#+begin_src shell :results value file link :file \"/tmp/test.txt\"
+echo \"hello\" > /tmp/test.txt
+echo \"test\"
+#+end_src"
+    (org-babel-execute-src-block)
+    (should (search-forward "[[file:/tmp/test.txt]]" nil t))
+    (should (with-temp-buffer
+	      (insert-file-contents "/tmp/test.txt")
+	      (string= "hello\n" (buffer-string)))))
+  ;; Without "link" output type, the result is not a file.
+  (should-not
+   (org-test-with-temp-text "
 <point>#+begin_src shell :results value link :file \"/tmp/test.txt\"
 echo \"hello\" > /tmp/test.txt
 echo \"test\"
 #+end_src"
-   (org-babel-execute-src-block)
-   (should (search-forward "[[file:/tmp/test.txt]]" nil nil))
-   (should (with-temp-buffer
-	     (insert-file-contents "/tmp/test.txt")
-	     (string= "hello\n" (buffer-string))))))
+     (org-babel-execute-src-block)
+     (search-forward "[[file:/tmp/test.txt]]" nil t))))
 
 (ert-deftest test-ob/result-graphics-link-type-header-argument ()
   "Ensure that the result is a link to a file.
 The file is just a link to `:file' value.  Inhibit non-empty
 result write to `:file' value."
   (org-test-with-temp-text "
+<point>#+begin_src shell :results value file graphics :file \"/tmp/test.txt\"
+echo \"hello\" > /tmp/test.txt
+echo \"test\"
+#+end_src"
+    (org-babel-execute-src-block)
+    (should (search-forward "[[file:/tmp/test.txt]]" nil nil))
+    (should (with-temp-buffer
+	      (insert-file-contents "/tmp/test.txt")
+	      (string= "hello\n" (buffer-string)))))
+  ;; Without "link" output type, the result is not a file.
+  (should-not
+   (org-test-with-temp-text "
 <point>#+begin_src shell :results value graphics :file \"/tmp/test.txt\"
 echo \"hello\" > /tmp/test.txt
 echo \"test\"
 #+end_src"
-   (org-babel-execute-src-block)
-   (should (search-forward "[[file:/tmp/test.txt]]" nil nil))
-   (should (with-temp-buffer
-	     (insert-file-contents "/tmp/test.txt")
-	     (string= "hello\n" (buffer-string))))))
+     (org-babel-execute-src-block)
+     (search-forward "[[file:/tmp/test.txt]]" nil t))))
 
 (ert-deftest test-ob/inline-src_blk-preceded-punct-preceded-by-point ()
   (let ((test-line ".src_emacs-lisp[ :results verbatim ]{ \"x\"  }")